Utility of immunohistochemistry with CK7 and CK20 in metastatic carcinoma

: Carcinoma of unknown primary origin (CUP) is a diverse group of cancers that is defined by the presence of metastatic disease with no identified primary tumor at initial presentation. Simple epithelium of the various organs is the most common source of the cancer. These carcinomas usually metastasize to lymph nodes and various other organs. Diagnosis of metastatic carcinoma of unknown origin can be challenging and also critical for clinical and therapeutic decisions. Immunohistochemistry (IHC) using CK7 and CK20 is an essential ancillary tool for the identification and the differential diagnosis of carcinomas of epithelial origin especially of undetermined primary. In this study we have aimed to evaluate the utility of immunohistochemistry by using CK7 and CK20 antibodies to identify the primary site in metastatic carcinoma. : This study included 70 histopathological cases with metastatic carcinoma received in Pathology laboratory in Bharati hospital over a period of two year. Metastatic carcinoma confirmed by histopathology examination and IHC using CK7 and CK20 was performed. : Total 70 cases examined for utility of CK7 and CK20 in metastatic carcinoma in various organs. Most common specimen was liver with metastatic carcinoma. Algorithmic IHC examination of CK7 and CK20 was done which showed CK7+CK20- pattern was the common pattern followed by CK7-CK20+. All cases of metastatic carcinoma lung, breast and thyroid followed CK7+CK20- pattern, 90% cases of colon carcinoma followed CK7-CK20+ pattern. However, Ovary, pancreas and gallbladder showed CK7+CK20- and CK7+CK20 pattern of expression. CK7-CK20- pattern was seen in cervical carcinoma, renal cases. : The study suggested that the combination of CK7 and CK20 was helpful in suggesting the likely primary site of malignancy.